The present invention relates generally to apparatus for protecting an operable computer digital data storage device from damage and loss of data resulting from fire or water exposure. More particularly, the present invention provides for the first time a compact, low cost, fire and/or water resistant enclosure for an operable computer digital data storage device. Typical computer digital data storage devices include computer hard drives, optical disk drives, solid state memory devices, tape drives, computers, or any other device which can actively read and write digital data with the intent of storing and retrieving computerized digital data. In the description below, reference is occasionally made simply to a hard drive as an example of a computer data storage device. It is to be understood that such a reference below is an example and not a limitation of the invention to hard drives.
As digital data storage devices become able to store staggering amounts of data, the loss of a digital data storage device in disasters such as fire or flood becomes more and more catastrophic. There is clearly a need to provide a compact, reliable fire and/or water resistant enclosure for operating digital data storage devices.
The present invention provides a compact, low cost, fire and/or water resistant enclosure for an operable computer digital data storage device. The phrase “fire resistant enclosure,” as used herein and in the claims, is hereby defined as an enclosure resistant to fire that occurs outside the enclosure. Fire resistance enclosures are designed to protect the contents inside the enclosure. The present invention differs from prior art “fire suppression enclosures” that are intended to suppress or to prevent the spread of fire that occurs within the enclosure, as for example in Blackmon et al, U.S. Pat. No. 6,548,753. Fire suppression enclosures are meant to protect the spread of fire to nearby objects outside the enclosure. As a result, fire suppression enclosures can be made of thin metal walls. On the other hand, fire resistant enclosures, such as the present invention, must include relatively thick, thermally insulating walls which incorporate insulation materials such as gypsum, ceramic fiber insulation or other possible fire resistant insulations. Enclosures made of thick, insulation filled walls filled with material such as gypsum present significantly different and more difficult design challenges than simple thin-walled metal enclosures.
The present invention includes several alternate embodiments, all of which are intended to provide low cost, reliable fire resistant and water resistant enclosures for operating hard drives and other computer data storage devices. The embodiments include, for example, hatchless enclosures with and without fans; water resistant enclosures with and without movable hatches; free convection enclosures with and without movable hatches, low cost enclosures molded of gypsum with integrally molded component supports; and enclosures with intumescent or meltable materials which, in the presence of fire, seal off passageways otherwise used to cool the data storage device.
A preferred embodiment of the present invention avoids the use of movable hatches, such as shown and described in U.S. patent application Ser. No. 11/112,552, referenced above, which application is hereby included herein by reference. The hatchless embodiment of the present invention also avoids the requirement of any fire or smoke sensing apparatus. Elimination of those components results in a significantly lower cost device. The linchpin for the preferred embodiment is the discovery that vents of a sufficiently small size formed in a relatively thick gypsum wall, for example, 1.5 inches thick, will prevent damage by fire while simultaneously allowing enough forced air ventilation in the absence of fire to cool the operating storage device! We have tested the concept with a prototype subjected to fire, with no loss of data and no serious damage to the hard drive storage device! We believe that as the internal air temperature starts to rise in the presence of fire, the internal air expands and flows outwardly through the small vent or vents. (The fan or blower that forces air through the vents loses power and stops operating at the outset of a fire.) The outward flow of expanding air counteracts the flow of external heat from the fire through the small vents into the internal chamber. The small vent or vents can be designed as tortuous or labyrinthian passages to reduce the amount of external heat from a fire that flows into the inner chamber. Examples are described below and shown in the drawings.
Our discovery is confirmed by the following calculation. Assuming constant atmospheric pressure, the internal volume of air will expand proportionally to the temperature rise in Kelvin (Tkelvin=Tcentigrade+273.15) according to the ideal gas theory and Boyle's Law [(P1V1)/T1=(P2V2)/T2]. Assuming an initial temperature of 298 K (25° C.) and a final temperature of 373 K (100° C.), the internal chamber volume of air is expected to increase by approximately 25%. Therefore, it is believed that 25% of the volume of air in the inner chamber will slowly flow outwardly through the vent or vents as the temperature of the inner chamber gradually increases by 75° C. By sizing the inner chamber and vents appropriately, we have discovered that an insulated and vented chamber can be sufficiently fire resistant to prevent loss of data from most fires!!
We are unaware of any prior art fire resistant enclosures for active data storage devices wherein vents in the walls remain open in the absence of fire and in the presence of fire. The prior art does include the Olzak et al U.S. Pat. No. 6,153,720 which teaches an aircraft recorder. The enclosure for the recorder includes vents which are normally closed but become opened in the presence of fire; a phase changing, heat absorbing layer melts and drains through the vents. The vents allow equalization of pressure if the recorder falls into the ocean. The Olzak et al enclosure does not teach or suggest forced air ventilation (or any ventilation) for an operating digital data storage device wherein significant amounts of heat are generated. It is simply not usable for the purpose of the present invention.
A second preferred embodiment of the invention includes a water resistant and heat conductive “pouch” (or covering) which surrounds the data storage device. The “pouch” and data storage device are both positioned inside a fire resistant enclosure. Heat generated by the data storage device is conducted through the “pouch” (preferably metal) and is thereafter transferred to the exterior of the fire resistant enclosure by a variety of techniques. The “pouch” is fully submersible and protects the device and stored data in up to 30 feet of water.
The prior art includes water and fire resistant enclosures for paper documents (see Gelb et al U.S. Pat. No. 4,992,310); however, such enclosures are wholly unsuitable for an operating computer data storage device. The prior art also includes cooling jackets for data storage devices, but the cooling jackets are not water resistant (see Cheon U.S. published application 2004/0190255).
The prior art includes a relatively large enclosure for operable digital data storage devices, such as the Engler U.S. Pat. No. 6,158,833, which dissipates heat generated by the digital data storage device by conduction through the insulated walls of the container. The Engler design requires a relatively large enclosure since it does not provide any active or fan-driven cooling system. The present invention, in contrast, provides a compact enclosure a fraction of the size of the Engler enclosure. The compact size of the present invention in one embodiment is achieved primarily because of a forced-air cooling system not present in the Engler device.
The prior art includes other digital data storage device enclosures with “passive” cooling systems, such as Pihl et al U.S. Pat. No. 5,479,341 which cools by convection through a partially open vent door. This technique is “free convection” because no fan or other active device is used to cause the convection. The Kikinis U.S. Pat. No. 5,623,597 utilizes a rather complex, passive heat exchanger with a rather large heat sink structure. That design requires a cumbersome insulation injection mechanism to fill the heat sink space when a threshold temperature is sensed. The present invention includes a “free convection” embodiment having a much simpler and more robust design than the prior art.
The prior art also includes the Kishon et al published U.S. application No. U.S. 2004/0064631 dated Apr. 1, 2004. The Kishon et al device utilizes passive conduction of heat generated by the data storage device through screws extending from ambient air to the device cover (see paragraph [0021]). This technique is limited by the relatively low amount of heat transferable through the metal screws. The active, fan-driven cooling provided by the present invention achieves a much greater cooling capacity.
The prior art also includes forced air cooling systems for operational digital data storage devices, but not used together with a compact, fire resistant enclosure.
A primary object of the invention is to provide a fire resistant and/or water resistant enclosure for an operable computer digital data storage device which is robust in design and inexpensive to produce.
A further object of the invention is to provide a fire resistant and water resistant enclosure for an operating data storage device having a hatchless enclosure which avoids the requirement of any fire or smoke sensing apparatus.
A further object of the invention is to provide a fire resistant enclosure for an operational digital data storage device utilizing vents of a sufficiently small size to prevent damage by fire while simultaneously allowing enough forced air ventilation to pass therethrough in the absence of fire to cool the operating storage device.
Another object of the invention is to provide a fire resistant enclosure for an active data storage device wherein vents in the walls of the enclosure remain open in the absence of fire and in the presence of fire.
A further object of the invention is to provide a fire resistant and water resistant enclosure for operating data storage devices molded of gypsum or other suitable molding material wherein mounts or components are integrally molded into the enclosure molding, itself.
Another object of the invention is to provide a fire resistant enclosure for an operational computer data storage device wherein an intumescent or meltable material is utilized to block passageways which otherwise provide ventilation for the data storage device.
A further object of the invention is to provide an enclosure for an operating computer data storage device wherein a heat conductive “pouch” surrounds the storage device, which is submersible and protects the data storage device and data stored therein in up to 30 feet of water.
Other objects and advantages of the invention will become apparent from the following description and drawings wherein: